Text Book Of Mechanical Engineering

Appendix VL

1013

The first rise of i % would correspond to the ' contraction allow-
ance ' of the pattern maker.

S

^-

— >

cc
01
f

0 0 x-
^
\ LINE
2. or
3 +e*u,M.
-q. ASMS!
S

TIME. is( N/UNUTE.S

sZ, Ir/oru

925.

CHAPTER III.

P. 76. Wrought Iron.—The following notes are given on
the authority of Mr. James P. Roe, of America, inventor of the
Roe puddling process :—

Puddling permits the use of pigs with very various composi-
tion, up to 3% Si, 3% P, 2|% Mn, or -35% S, though not all in
the same pigs; but the best proportions are i% Si, less than
i% P, -i% S, and '5% Mn. The wrought iron produced is free
from red or cold shortness, and is very weldable. The flux being
roll-scale, ore, or oxidising gas, is for the purpose of abstracting
the C as already described, and forms the * cinder,' which when
low produces the greatest strength, but when high gives very free
welding power. The subsequent piling and reheating is for the
purpose of removing this cinder to the desired extent.

In the final structure of the metal each grain or crystal is
surrounded by an envelope of cinder (ferrous silicate), the greater
part of which, however, is eliminated by hammering and rolling,
arrd a fibrous structure results, which is the real source of strength